Contaminates such as rust particles and metal shavings can become dislodged from the interior of the engine and enter and clog or restrict flow through the radiator of the engine cooling system. When the radiator becomes plugged, costly engine and radiator repairs can result. In addition, because the engines are often installed on expensive commercial equipment, engine down time can result in significant economic losses as well. It would be a benefit, therefore, to have a filter assembly that could be installed between the engine and the radiator of the engine cooling system that could trap contaminants before they entered the radiator. In addition, because the clogging of the filter assembly itself could result in damage to the engine, it would be desirable if the filter element within the filter assembly were easily checked and replaced when necessary. It would be a further benefit if the filter assembly included a pressure relief valve in order to vent high pressure within the engine cooling system prior to replacement of the filter element.